Highly confined electromagnetic fields in arrays of strongly coupled Ag nanoparticles

L. A. Sweatlock, S. A. Maier, H. A. Atwater, J. J. Penninkhof, and A. Polman
Phys. Rev. B 71, 235408 – Published 10 June 2005

Abstract

Linear arrays of very small Ag nanoparticles (diameter 10nm, spacing 04nm) were fabricated in sodalime glass using an ion irradiation technique. Optical extinction spectroscopy of the arrays reveals a large polarization-dependent splitting of the collective plasmon extinction band. Depending on the preparation condition, a redshift of the longitudinal resonance as large as 1.5eV is observed. Simulations of the three-dimensional electromagnetic field evolution are used to determine the resonance energy of idealized nanoparticle arrays with different interparticle spacings and array lengths. Using these data, the experimentally observed redshift is attributed to collective plasmon coupling in touching particles and/or in long arrays of strongly coupled particles. The simulations also indicate that for closely coupled nanoparticles (12nm spacing) the electromagnetic field is concentrated in nanoscale regions (10dB radius: 3nm) between the particles, with a 5000-fold local field intensity enhancement. In arrays of 1nm-spaced particles the dipolar particle interaction extends to over 10 particles, while for larger spacing the interaction length decreases. Spatial images of the local field distribution in 12-particle arrays of touching particles reveal a particlelike coupled mode with a resonance at 1.8eV and a wirelike mode at 0.4eV.

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  • Received 1 December 2004

DOI:https://doi.org/10.1103/PhysRevB.71.235408

©2005 American Physical Society

Authors & Affiliations

L. A. Sweatlock*, S. A. Maier, and H. A. Atwater

  • Thomas J. Watson Laboratory of Applied Physics, California Institute of Technology, Pasadena, California 91125, USA

J. J. Penninkhof

  • Center for Nanophotonics, FOM-Institute AMOLF, Kruislaan 407, 1098 SJ Amsterdam, The Netherlands

A. Polman

  • Thomas J. Watson Laboratory of Applied Physics, California Institute of Technology, Pasadena, California 91125, USA and Center for Nanophotonics, FOM-Institute AMOLF, Kruislaan 407, 1098 SJ Amsterdam, The Netherlands

  • *Electronic address: lukes@caltech.edu

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Issue

Vol. 71, Iss. 23 — 15 June 2005

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